Field of the Invention
The present invention relates to a polymer compound for a conductive polymer and a method for producing the same.
Description of the Related Art
A polymer containing a sulfo group has been used as a fuel cell or a dopant polymer for a conductive polymer. As a material for a fuel cell, vinyl-perfluoroalkyl ether sulfonic acid represented by Nafion (registered trademark) has been widely used, and as a dopant polymer for a conductive polymer, a polymer of vinylsulfonic acid or styrenesulfonic acid has been widely used (Patent Document 1). Patent Document 2 proposes a fluorinated acid polymer in which protons are substituted by cations as a dopant polymer, and also reveals a dopant of a styrene derivative having a lithium salt of bisfluoroalkylsulfonylimide.
The vinylperfluoroalkyl ether sulfonic acid has chemically high stability and excellent durability, but the glass transition point thereof is low, so that there is a problem that when a fuel cell using it is exposed to high temperature, the polymer causes heat flow whereby ion conductivity thereof is lowered. The bisfluoroalkylsulfonylimide-containing styrene derivative has the same problem. A superacidic polymer having a sulfo group an α-position of which has been fluorinated is effective for enhancing the ion conductivity, but a material having high glass transition point and chemical stability with such a structure has not yet been found out.
Also, a conductive polymer having a conjugated double bond such as a polythiophene, a polyaniline, a polypyrrole, etc., does not exhibit conductivity itself, but conductivity thereof is expressed by doping therein a strong acid such as sulfonic acid, etc. As the dopant, polystyrene sulfonic acid (PSS) has been most frequently used. This is because conductivity becomes the highest by doping PSS.
PSS is a water-soluble resin, and hardly dissolves in an organic solvent. Accordingly, a polythiophene using PSS as a dopant is also water-soluble.
The polythiophene using PSS as a dopant is highly conductive and highly transparent, so that it has been expected to be used as a conductive film for an organic EL lighting in place of ITO (indium-tin oxide). However, a luminous body of the organic EL chemically changes by moisture, thereby stopping to emit a light. That is, when a conductive film composed of a water-soluble resin is used for an organic EL, there is a problem that an emission lifetime of the organic EL becomes short due to the resin containing water.